Systems and methods for accurately measuring fluid

ABSTRACT

The present invention relates to systems and methods for measuring the amount of fluid. A fluid source is in fluid communication with a measuring system. The fluid source includes a non-collapsible walled container for dispensing or introducing fluid. The measuring system includes a sensor in fluid communication with the container that senses the volume of the gas, and a system that calculates the amount of fluid flowing through an opening of the container based on the amount of gas flowing through an opening of the container. The volume of gas entering or exiting the container is measured rather than directly measuring the amount of fluid leaving or entering the container to determine in a more accurate, less complicated and less expensive manner the volume of fluid.

RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/785,656, filed Feb. 16, 2001, entitled “SYSTEMS AND METHODSFOR ACCURATELY MEASURING FLUID,” which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. The Field of the Invention

[0003] The present invention relates to systems and methods foraccurately measuring an amount of fluid. More specifically, the presentinvention is directed to systems and methods for using a measurement ofthe amount of gas to measure, in a sterile, reliable and accuratemanner, the amount of fluid that is dispensed from or introduced into acontainer.

[0004] 2. Background and Related Art

[0005] Since the beginning of science, practitioners have been requiredto measure the amount of liquid transferred from one container toanother container or location. Traditional methods for performing suchliquid transfer measurements have included the use of such devices asmeasuring cups or liquid flow meters. While each method has its owndistinct and unique advantage, a number of drawbacks exist in theutilization of the traditional methods for measuring liquid transferredor dispensed from a container. As an example, the traditional methodscan expose the transferred liquid to impurities within the environment,such as air-born bacteria, and allow for the introduction of human errorinto the measurements. The methods can also be complex and expensive,and unable to accurately measure low volumes of liquids due to varyingdensities and viscosities.

[0006] Additional drawbacks are specific to the application for whichthe liquid transfer measurements are being performed. By way of example,one area where practitioners are required to accurately measure theamount of liquid transferred or dispensed from a container is in themedical area of radiology, in which a radiopaque liquid known as“contrast medium” is inserted into a patient's body so as to provide acontrast in density between the area of the body that is being x-rayedand the contrast medium inserted.

[0007] When fluid, such as contrast medium, is intravenouslyadministered, it is critical that air bubbles are not inadvertentlyintroduced into the patient's vascular system. It is, therefore,important that the practitioner monitor and continually assess theamount of medium remaining in the container in order to prevent anypossibility of inadvertently injecting air bubbles into the patient.Administering an excess amount of fluid, such as contrast medium, canalso injure a patient. Due to the current expense of contrast medium, itis also very important for the practitioner dispensing the contrastmedium to perform the process in a manner that results in the leastamount of waste. For accurate billing and cost assessment purposes, apractitioner is required to monitor the exact amount of contrast mediumthat is delivered to each patient over the course of the patient'smedical procedure or hospital stay. However, monitoring the exact amountof contrast medium administered to a patient is difficult, particularlywhen multiple contrast medium dispensers are used or when a dispenser isshared between two patients. This inability to accurately monitor theexact amount of medium administered can result in patients beingincorrectly charged. The inaccuracies complicate any determination as tothe amount of useful medium remaining in a dispenser and often result inthe remainder being discarded rather than being used on a new patient.Given the high cost, such waste of contrast medium can translate intosignificant financial losses for facilities that perform a large numberof these fluid-dispensing procedures.

[0008] This need to accurately measure the amount of contrast mediumdispensed is one example of the current need to accurately and reliablymeasure liquid that is dispensed from a container.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to systems and methods forusing a measurement of the amount of gas entering or exiting a containerto measure, in a sterile, reliable and accurate manner, the amount offluid that is dispensed from or introduced into a container.

[0010] Implementation of the present invention is performed inassociation with a non-collapsible container. The container comprises arigid material such that as fluid is dispensed from the container and avacuum is created, the container walls do not collapse. A measuringsystem that includes a sensor is in fluid communication with thecontainer.

[0011] In one implementation of the present invention, a sensor is usedfor sensing the volume of the gas entering or exiting the container. Thesensor can be a single sensor that performs both functions of sensingboth the mass flow and the density of the gas, or can be a dual sensorwherein one sensor component senses the mass flow and another sensorcomponent senses the density. Optionally, a measurement of the gasdensity can be preprogrammed into the sensor or calculating system suchthat the sensor only senses gas flow. The volume of gas entering orexiting the container may also be measured in a variety of differentmanners.

[0012] The calculating system calculates the amount of fluid dispensedfrom or introduced into the container based on the amount of gas flowinginto or out of the container. The calculating system typically comprisesan electrical system that includes a microprocessor and/or ananalog-to-digital converter, but can comprise a variety of differentsystems, such as a mechanical system that determines the amount of gasflowing due to fluid dispensed from or introduced into a container. Thefluid may comprise a liquid, such as contrast medium or a variety ofdifferent fluids.

[0013] A filtering system may optionally be used to maintain a sterileenvironment and to protect the sensor. Therefore, in light of theoverall system, the gas entering or exiting the container is measuredrather than directly measuring the amount of fluid leaving or enteringthe container, causing the measurement to be more accurate, lesscomplicated, and less expensive.

[0014] Additional features and advantages of the invention will be setforth in the description that follows, and in part will be obvious fromthe description, or may be learned by the practice of the invention. Thefeatures and advantages of the invention may be realized and obtained bymeans of the instruments and combinations particularly pointed out inthe appended claims. These and other features of the present inventionwill become more fully apparent from the following description andappended claims, or may be learned by the practice of the invention asset forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to describe the manner in which the above-recited andother advantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

[0016]FIG. 1 illustrates a syringe in fluid communication with a fluidsource that dispenses fluid to the syringe and is in fluid communicationwith a calculating system that calculates the volume of fluid dispensed;and

[0017]FIG. 2 is a flow chart that illustrates an exemplary embodimentfor calculating the volume of fluid dispensed from a container based onmass flow and density measurements of gas that enters the container dueto the fluid being dispensed.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention extends to systems and methods formeasuring the amount of fluid. More specifically, the present inventionis directed to systems and methods for using a measurement of a volumeof gas to measure, in a sterile, reliable and accurate manner, thevolume of fluid that is dispensed from or introduced into a container.The embodiments of the present invention may comprise a fluid sourcecoupled in fluid communication to a calculating system, as will bediscussed in greater detail below.

[0019] Throughout the disclosure, reference is made to calculating thevolume of fluid based on the amount of gas that flows through an openingof a container as a result of fluid flowing through an opening of acontainer. In the disclosure and in the claims the term “gas” refers toany type of gas or combination of gasses that are allowed to enter thefluid source. As such, the term “gas” may refer to hydrogen, helium,nitrogen, oxygen, or any other gas or a combination of gases, includingair, for example. Furthermore, in the disclosure and in the claims, theterm “opening” may refer to any aperture or channel, including a portcoupled to or integral with the container, for example, through whichgas and/or fluid can flow.

[0020] Embodiments of the present invention comprise a gas source, afluid source and a measuring system. In one embodiment, the gas sourceincludes a tank or container having a gas therein. In anotherembodiment, the gas source is the surrounding atmospheric environmentand the gas contained therein is the atmospheric air.

[0021] The fluid source includes a non-collapsible walled containerhaving fluid therein. The gas source is coupled in fluid communicationwith the fluid source so as to allow gas from the gas source to enter orexit the fluid source as fluid flows. In one embodiment, the measuringsystem is interposed between the gas and fluid sources and measures themass flow and density of the gas that is transferred between the gassource and the fluid source so as to calculate the amount of fluiddispensed from the fluid source based on the volume of gas flowing intothe fluid source. As such, in accordance with the present invention, theamount of fluid dispensed is measured in a more accurate, lesscomplicated, and less expensive manner.

[0022] With reference now to FIG. 1, an example of a suitableenvironment in which the invention may be implemented is provided. Whilethe embodiment of FIG. 1 illustrates a fluid dispensing system 100 thatmay be used in connection with a fluid delivery system 140, thoseskilled in the art will appreciate that the present invention may bepracticed in a variety of system configurations that include a fluidsource, a gas source, and some kind of a measuring system so as tomeasure the amount of fluid dispensed.

[0023] In FIG. 1, an exemplary system for implementing the presentinvention is illustrated as fluid dispensing system 100, which includesa measuring system 120 interposed between a gas source 110 and a fluidsource 130. As fluid is dispensed or displaced from fluid source 130,gas flows from gas source 110, through measuring system 120, and intofluid source 130, as will be further explained below.

[0024] Gas source 110, may be any type of gas supply that contains gastherein, including a tank, a container and/or the atmosphericenvironment. In an embodiment where gas source 110 is an enclosed tankor container having gas stored therein, gas source 110 is coupled influid communication with measuring system 120. In an alternativeembodiment, where gas source 110 is the atmospheric environmentsurrounding the fluid dispensing system 100, a gas inlet port coupled tothe measuring system 120 allows air to enter into the measuring system120.

[0025] Measuring system 120 senses the volume of gas entering acontainer of the fluid source as fluid is dispensed therefrom andthereby calculates the volume of fluid dispensed. In the embodiment ofFIG. 1, measuring system 120 comprises a sensor for sensing the massflow and density of the gas entering a container 132 of the fluid source130. The sensor of the present invention can be a single sensor thatperforms both functions of sensing the mass flow of gas and the densityof gas, or can be a dual sensor wherein one sensor component senses themass flow of gas and another sensor component senses the density of gas.Optionally, a measurement of the gas density can be preprogrammed intothe sensor or the calculating system such that the sensor only sensesthe mass flow of the gas, as will be further explained below.Optionally, the volume of gas entering the container may be measured ina variety of different manners.

[0026] In FIG. 1, the sensor is a dual sensor wherein one sensorcomponent is illustrated as sensor 122, which is in fluid communicationwith an inlet port 121 a and an outlet port 121 b, and another sensorcomponent is illustrated as density sensor 123. Sensor 123 measures thedensity of the air or other gas. Gas from gas source 110 (e.g., air)enters inlet port 121 a, flows through sensor 122, and exits outlet port121 b. As the gas flows through sensor 122, the mass flow of the gas ismeasured. Sensor 122 is an example of a means for sensing the amount ofgas flowing. While sensor 122 may be any sensor that measures the massflow of gas, in the illustrated embodiment sensor 122 is a mass flowmeter. By way of example, one mass flow meter that may be used as sensor122 is an AWM3000 series mass airflow sensor that is available fromHoneywell Inc., 11 West Spring Street; Freeport, Ill. 61032. Sensor 123may comprise a barometer or altimeter, for example.

[0027] As illustrated in FIG. 1, measuring system 120 may furthercomprise a calculating system 124 that is in communication with sensor122. Calculating system 124 is an example of a means for calculating theamount of fluid displaced and may comprise one or more mechanical and/orelectrical systems that are used to calculate the amount of gas thatenters fluid source 130 based on a measurement of the mass flow of gasthrough sensor 122 and a measurement of the density of the gas. In theillustrated embodiment, the measurement for the mass flow of gas isobtained by sensor 122 and the measurement for the density of gas isobtained by density sensor 123. Both the measurement of the mass flow ofgas and the density of gas are transmitted to calculating system 124.Optionally, calculating system 124 is preprogrammed with a measurementof the density of the gas. Sensor 123 and a preprogrammed calculatingsystem 124 are each examples of means for obtaining a density value of agas.

[0028] An electrical system of calculating system 124 may comprise ananalog-to-digital converter and/or a special purpose or general purposecomputer including various computer hardware and/or software forcalculating the amount of gas flowing into a fluid source. Calculatingsystem 124 may further include a computer-readable medium for carryingor having computer-executable instructions or data structures storedthereon that can be accessed by a general purpose or special purposecomputer. Computer-executable instructions comprise, for example,instructions and/or data structures that cause a general purposecomputer, special purpose computer, or special purpose processing deviceto perform a certain function or group of functions, such as calculatingthe amount of gas flowing into a fluid source.

[0029] Those skilled in the art will appreciate that calculating system124 may comprise computing environments with many types of computersystem configurations, such as a personal computer, calculator,hand-held device, multi-processor system, microprocessor-based orprogrammable consumer electronic device, a network PC, minicomputer,mainframe computer, or one or more similar devices, for example. In oneembodiment, calculating system 124 comprises a general purpose computingdevice in the form of a conventional computer that is coupled to anoutput device 126, such as a monitor, printer, speaker or other outputdevice. Output device 126 is an example of a means for informing a userof the amount of fluid displaced and may include a visual and/or audiblenotification to inform a user as to the amount of fluid displaced oralternatively the amount of fluid available for displacement.Furthermore, calculating system 124 may operate in a networkedenvironment using logical connections to one or more remote computers.

[0030] Fluid source 130 is coupled in fluid communication to measuringsystem 120 and includes a container 132 having fluid therein. Container132 is an example of a non-collapsible means for containing fluid. Inthe illustrated embodiment, container 132 is a non-collapsible walledcontainer that comprises a rigid material. Examples of such rigidmaterials include glass, plastic, metal, wood, or any other materialthat is non-deformable such that as the fluid is dispensed from thecontainer and a vacuum is created, the container walls do not collapse.

[0031] Coupled to container 132 are one or more ports. The ports allowfor fluid to be dispensed or displaced from container 132 and gas toenter into container 132. In the illustrated embodiment, a vented spike134 is coupled to container 132 to provide the one or more ports. Thevented spike 134 includes a gas inlet port 136 and a fluid outlet port138, each of which is configured to be placed in fluid communicationwith a container connection port 137 configured to be in fluidcommunication with container 132. Gas inlet port 136 is configured to bein fluid communication with sensor 122, port 138 is configured to be influid communication with fluid delivery system 140, and port 137 isconfigured to be in fluid communication with container 132.

[0032] By way of example, a type of vented spike that may be used asspike 134 to allow liquid to dispense from container 132 and gas toenter container 132 is a Burron OEM vented piercing device, aka a dualflow piercing device, available from Burron OEM, a division of B. BraunMedical, Inc., 824 12^(th) Avenue, Bethlem, Pa. 18018.

[0033] Spike 134 allows gas to enter container 132 through port 137while fluid exits container 132 and flows into fluid delivery system 140through port 138. Nevertheless, while FIG. 1 illustrates a vented spikehaving a fluid outlet port, a container port and a gas inlet port, avariety of one or more ports may be employed to allow the fluid todispense from container 132 and gas to enter into container 132. By wayof example, one port may be employed for both the inflow of gas andoutflow of fluid. Alternatively, a plurality of ports may be utilized,including one or more gas inlet ports coupled in fluid communication tocontainer 132 and one or more fluid outlet ports coupled in fluidcommunication to container 132. A plurality of gas inlet ports and/or aplurality of fluid outlet ports may be utilized, or any othercombination of one or more ports to allow fluid to dispense fromcontainer 132 and gas to enter into container 132. By way of example,the fluid container may comprise a vented bottle having a non-ventedspike coupled thereto.

[0034] As fluid is dispensed from fluid source 130, gas is transferredfrom gas source 110, through measuring system 120 and into fluid source130. The transfer of the gas occurs from a hydrostatic pressure in thefluid source 130 that causes the gas to flow from gas source 110, andinto fluid source 130. As the gas flows through the measuring system120, the flow and density of the gas flowing therethrough is obtained tocalculate the amount of fluid dispensed based on the amount of gasflowing into the fluid source 130.

[0035] To provide for and maintain a sterile environment, fluiddispensing system 100 may optionally include a filtering system coupledto sensor 122 in order to eliminate any impurities present in the gas.In the illustrated embodiment, the filtering system comprises filters128 a, 128 b and 133, where filter 128 a is coupled at inlet port 121 a,filter 128 b is coupled to outlet port 121 b, and filter 133 is coupledto gas inlet port 136 of fluid source 130. While the filtering systemillustrated in FIG. 1 includes three filters, embodiments of the presentinvention include filtering systems having more than three filters orless than three filters.

[0036] When fluid is dispensed from the fluid source 130, hydrostaticpressure in fluid source 130 causes gas to be transferred from the gassource 110, through the measuring system 120 and into the fluid source130. As the gas flows through the measuring system 120, an amount of gasflowing therethrough is measured to calculate the volume of fluiddispensed based on the volume of gas flowing into the fluid source 130.

[0037] While the embodiment of FIG. 1 illustrates a fluid dispensingsystem, embodiments of the present invention also embrace systems andmethods for calculating a volume of fluid introduced into a container.In such embodiments, the measuring system calculates the volume of fluidintroduced by sensing the flow of air exiting the container as fluid isintroduced. Furthermore, embodiments of the present invention alsoembrace systems and methods for calculating the volume of fluiddispensed and introduced by sensing air flow. By way of example, abi-directional sensor may be employed to sense the flow of air into orout of the container due to the respective flow of fluid out of or intothe container. Such systems are particularly useful when the fluid is,for example, an expensive fluid and any portion of the fluid that isdispensed from the container but has remained unused (i.e. remained inthe sterile environment) can be saved by being introduced back into thecontainer. As such, a total volume of fluid can be obtained even afterfluid is dispensed and then re-introduced into the container. Therefore,the systems and methods of the present invention accurately calculate anamount of fluid dispensed and/or introduced.

[0038] In one embodiment, the calculating system calculates the amountof fluid dispensed as depicted and discussed with reference to the flowchart of FIG. 2. In one embodiment, the gas source 110 is theatmospheric air and density sensor 123 measures the density of theatmospheric air while sensor 122 measures the mass flow of the airflowing therethrough.

[0039] In FIG. 2, execution begins at decision block 150 where adetermination is made 20 as to whether or not the components of themeasuring system have been zeroed. The process of zeroing (e.g.,initializing) components that are used to obtain measurements canprovide a more accurate measurement, and is more fully described in U.S.Pat. No. 5,807,321, entitled SYSTEM FOR ELECTRONICALLY MONITORING THEDELIVERY OF CONTRAST MEDIA, filed Sep. 15, 1998, which is incorporatedherein by reference. If it is determined at decision block 150 that thecomponents of the measuring system have been zeroed, execution proceedsto decision block 154. Alternatively, if it is determined that thecomponents of the measuring system have not been zeroed, executionproceeds to step 152 for the automatic zeroing of the components of themeasuring system and execution then proceeds to decision block 154.

[0040] At decision block 154, a determination is made as to whether ornot the density of gas has been measured or provided. By way of example,the units of the density of gas are mass per volume (e.g., g/cc). Asprovided above, the density of gas may be measured by the same sensorcomponent that measures the mass flow of gas or by a separate densitysensor component. If it is determined at decision block 154 that thedensity of gas has been measured, execution proceeds to step 158.Alternatively, if the density of gas has not been measured, executionproceeds to step 156, where a value is obtained for the density of thegas and then execution proceeds to step 158.

[0041] At step 158, dispensing of the fluid contained within thenon-collapsible walled container begins. The dispensing of the fluidcauses a hydrostatic pressure within the non-collapsible walledcontainer to change, resulting in gas flowing from the gas source,through the measuring system and into the non-collapsible walledcontainer of the fluid source. As the gas flows, the mass flow of gas ismeasured by a sensor at step 160 and is communicated to the calculatingsystem. The units of the mass flow of gas are, for example, grams persecond (g/s). At step 162, the mass flow of gas measurements obtained atstep 160 are received by the calculating system, which calculates theamount of fluid dispensed from the non-collapsible walled container ofthe fluid source based on the mass flow and the density of the gas.

[0042] At step 164, the calculating system eliminates any gas densityoffset from the measurements obtained at step 160 of the mass flow ofgas. For example, dividing the mass flow (e.g., g/s) by the density(e.g., g/cc) to yield flow (e.g., cc/s) eliminates the density offset.At times, the volume flow of fluid (e.g., cc/s) is what is desired to beoutput on an output system. In such instances, the flow of gas (e.g.,cc/s) obtained at step 164 corresponds to the volume flow of fluid(e.g., cc/s) and is thus output on an output system at step 168. By wayof example, volume flow can be calculated as depicted in Equation 1below. $\begin{matrix}{\text{Volume~~Flow} = {\frac{massflow}{density} = {\frac{\frac{g}{s}}{\frac{g}{cc}} = \frac{cc}{s}}}} & \text{Equation~~1}\end{matrix}$

[0043] Alternatively, it may be desired to obtain the total volume offluid. Therefore, once the flow of gas (e.g., cc/s) is obtained at step164, execution proceeds to step 166 to calculate the total volume of gas(e.g., cc), which corresponds to the total volume of fluid.

[0044] At step 166, the volume of the gas that entered into thenon-collapsible walled container is calculated. While the volume of gascan be calculated in a variety of manners, one way of calculating thevolume is illustrated by the present example and includes obtaining theparameters of mass flow (step 160) and density of the gas (step 156),eliminating a density offset (step 164), and at step 166 integratingwith respect to time the gas flow obtained at step 164. The volume ofthe gas that entered into the non-collapsible walled containerrepresents the volume of fluid dispensed therefrom. By way of example,the total volume may be calculated as depicted in Equation 2 below.$\begin{matrix}{\text{Total~~Volume} = {{\int{\text{Volume~~Flow} \cdot {t}}} = {{\int{\frac{cc}{s} \cdot {t}}} = {cc}}}} & \text{Equation~~2}\end{matrix}$

[0045] Execution then proceeds to step 168 for outputting (e.g.,displaying, broadcasting, transmitting, etc.) the total volume of fluiddispensed on a display screen, digital display, or other output system.The volume of fluid dispensed may be displayed in a variety of manners,including graphically, by percentage, pictorially, or otherwise.Furthermore, the display screen or other output system may display thevolume of fluid dispensed from the fluid source, the volume of fluidcurrently available in the fluid source, the volume delivered to aparticular patient, etc.

[0046] Thus, the present invention extends to both systems and methodsfor measuring the amount of fluid dispensed from and/or introduced intoa fluid source through the utilization of the flow and density of gas.The present invention may measure liquid such as a contrast medium, orother liquids, gasses, or fluids. A practitioner or user can thereforeknow at any given instant in time the amount of liquid (such as acontrast medium or other fluid) that has been dispensed from a fluidsource and the amount of fluid still available in the fluid source.Furthermore, the systems and methods of the present invention measureand obtain the amount of fluid in a sterile, reliable and accuratemanner.

[0047] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed and desired to be secured by United States LettersPatent is:
 1. A system for containing fluid and for determining anamount of fluid flow, the system comprising: a non-collapsible means forcontaining fluid; means for sensing an amount of gas flowing through anopening of said means for containing fluid as fluid flows through anopening of said means for containing fluid, wherein said means forsensing is in fluid communication with said means for containing fluid;and means for calculating the amount of fluid flowing through an openingof said means for containing fluid based on the amount of gas flowingthrough an opening of said means for containing fluid, wherein saidmeans for calculating is coupled to said means for sensing.